With "relative pressure", "relative vacuum level" (ie than the "atmospheric" How much pressure is low) to represent:

The relative degree of vacuum pressure refers to the object under test and measurement locations atmospheric pressure difference, measured with an ordinary vacuum table. In a state where there is no vacuum (i.e., when atmospheric pressure), the initial value 0 in Table. When measuring the vacuum, its value between 0 -101.325KPa between (usually with a negative number indicates).

International Vacuum common industry "vacuum degree", is identified by the absolute pressure; refers to the "ultimate vacuum, absolute vacuum, absolute pressure." But "relative vacuum degree" (relative pressure, vacuum pressure exemplar, negative) as a result of the measurement method is simple, measuring instruments are very common, readily available and inexpensive, it is also widely used. Both are theoretically can be converted to each other, the two conversion methods are as follows:

What is the vacuum
Vacuum means that a given gas pressure within the space of less than the area of a standard atmospheric pressure gas state.
Vacuum is rarefied gas environment. Compared with the atmosphere it has a number of advantages, such as gas thin, less oxygen, clean environment...

Vacuum pump in a variety of different job categories effect have?
Vacuum pumps work in a variety of different play areas in effect summed up in the following areas:
1, main pump: the so-called main pump is a vacuum system is evacuated container is directly evacuated to the vacuum pump ...